A liquid crystal display (LCD) generally comprises two opposed electrode substrates, a spacer, as interposed therebetween, and a liquid crystal substance. The spacer serves to get the thickness of a liquid crystal layer uniform over the planar entirety of the layer by keeping the interval between the two electrode substrates constant over the planar entirety of the electrode substrates.
Generally, high speed of response, high contrast, a wide viewing angle, etc. are among display performance characteristics cited as such as demanded in practical use of the liquid crystal display. For these performance characteristics to be realized, the thickness of the liquid crystal layer, namely, the gap distance between the two electrode substrates, must be kept strictly constant.
A process for producing a liquid crystal display is, for example, carried out in the following way: a particle for the liquid crystal display is first dispersed onto one of the substrates uniformly so that the particle may not aggregate; and the dispersed particle is then covered with the other substrate.
Conventionally, the dispersion of the particle is carried out in a wet manner. The wet manner is, for example, a manner in which a substrate is sprayed with a dispersion which is prepared by dispersing a spacer particle into a solvent such as flon, alcohol, or a water-alcohol-mixed solvent. The wet manner, however, has problems, for example, in the following respects: regulation against flon; environmental contamination and flaming due to organic solvents; and damage or contamination to an oriented membrane due to solvents.
Therefore, recently, the dispersion in the wet manner is being replaced with that in a dry manner. The dry manner is a manner in which a spacer particle is directly dispersed onto a substrate with a compressed gas such as nitrogen. For example, a dry manner is proposed which utilizes a high speed gas stream manner or an electrostatic dispersion manner. The high speed gas stream manner is a manner in which: a predetermined amount of spacer particle is electrified by friction through pipes, and the spacer particle is then vomited from a nozzle to a substrate. In addition, the electrostatic dispersion manner is a manner in which a spacer particle is vomited from a high-voltage-applied nozzle to an earthed substrate.
The dry dispersion manner is excellent in that no solvent is used, and this manner is often applied to a TFT-LCD. However, this manner has another problem in that the particle aggregates when dispersed, because no solvent is used. Where the dispersed particle aggregates, it is difficult to keep the gap distance between electrode substrates constant, and "leakage of the light of a backlight lamp" therefore occurs in that the area where no image is partially formed increases. As a result, the image display quality becomes low.
By the way, the above-mentioned leakage of the light of a backlight lamp is also caused by that the orientation of a liquid crystal on the periphery of the spacer is disordered due to interactions between liquid crystal molecules and a surface of the spacer particle, and by that somewhat of a space which transmits the light is therefore formed on the periphery of the spacer. Recently, the display area is getting larger and larger (e.g., 12 inches or more) in the uses for televisions, monitors, notebook type personal computers, word processors, etc. In addition, the display area is also getting larger and larger in the uses for car navigation systems, televisions, etc., as equipments for cars. Accompanying such enlargement of the display area, vibration or impact as given to the liquid crystal display becomes larger, so the leakage of the light of a backlight lamp from the periphery of the spacer further increases in area. As a result, the image display quality of the liquid crystal display is liable to deteriorate. Thus, it is important that the leakage of the light of a backlight lamp from the periphery of the spacer does not increase even if vibration or impact is given to the liquid crystal display.
In a conventional method for preventing such leakage of the light of a backlight lamp from the periphery of the spacer, a surface of the spacer particle is treated with vertical-orientation treatment agents such as alkyltrialkoxysilanes. It was, however, found that: where such a treatment is made, the spacer particles might easily aggregate together and show bad dry dispersibility, and as a result, the leakage of the light of a backlight lamp due to the aggregation of the particle increases, and the image display quality therefore deteriorates.